Character input device using bio radar unit and tilt sensor

1. A character input device for a mobile device or a wearable terminal, comprising: a bio radar unit configured to transmit a signal toward a fingertip of a finger of a user and to measure the strength of a signal reflected from the fingertip; a tilt sensor configured to sense a tilt of hands of the user; a microprocessor configured to calculate final input information of the user by processing signals received from the bio radar unit and the tilt sensor; and a wireless communication module configured to transmit the final input information to the mobile device or the wearable terminal of the user, wherein, the microprocessor is configured to calculate a direction of the finger, based on a ratio between a total scan period of the bio radar unit and a period of time taken to perceive the fingertip, and to calculate a distance to the fingertip, based on the strength of the reflected signal, the microprocessor is configured to detect the input of a special key according to the tilt measured by the tilt sensor, the microprocessor, when three or more of the fingers are detected as input, is configured to process this case as a character input error and not determine the input character, the microprocessor, when two of the finders are detected as input, is configured to detect fingertip thickness information of each of the fingers, and to obtain final input information by comparing the detected fingertip thickness information to the fingertip thickness information of the reference information, when α a ≥ β b , a finger corresponding to ‘a’ is detected as input information and when α a < β b , a finger corresponding to ‘b’ is detected as input information, where a and b represent reference fingertip thickness information for the two fingers, and α and β represent detected fingertip thickness information.

2. The character input device as set forth in claim 1 , wherein the character input device is formed to be wearable on a wrist of the user.

3. The character input device as set forth in claim 1 , further comprising a speaker device configured to output a feedback sound corresponding to the final input information of the user.

4. The character input device as set forth in claim 1 , wherein the bio radar unit is configured to measure the direction of the finger by detecting an angle of the finger relative to the bio radar unit.

5. The character input device as set forth in claim 1 , wherein the microprocessor, when no input activation is performed by a finger, is configured to detect the input of the special key, based on the following table: Left Hand Right Hand Tilt Special Key Tilt Special Key ↑ Home ↑ Up ↓ End ↓ Down ← Back Space ← Left → Space → Right Both Left and Right Hands ↑ Page Up Both Left and Right Hands ↓ Page Down.

6. The character input device as set forth in claim 1 , wherein the microprocessor is configured to previously store reference information, comprising coordinate values corresponding to respective positions of keys on a virtual keyboard, initial range values detectable based on positions of fingers of the user, and fingertip thickness information obtained when fingers are placed on the keys of the keyboard, and to determine an input character by comparing the stored reference information with the detected input information.